Shaping and Instinctive Drift

Operant conditioning works by reinforcing behavior after it happens, but some behaviors are so complex or unlikely that an animal may never perform them on its own to be rewarded. Shaping solves this by reinforcing successive approximations: responses that are closer and closer to the final target behavior. A trainer starts by rewarding something crude that resembles the goal, then raises the bar, withholding reinforcement for the old response and waiting for something slightly closer. Each new approximation becomes the new baseline, until only the full target behavior earns the reward. This is how trainers get pigeons to turn in circles or push levers in sequences they would never stumble into naturally.

Instinctive drift is the catch. Even after a behavior is well trained, an animal's hardwired, species-typical instincts can creep back in and override the learned response, especially when the task involves objects or motions tied to natural behaviors like foraging or food-handling. A raccoon trained to deposit coins starts rubbing and dropping them because that mimics its instinct to wash food. The reinforcement schedule hasn't changed; the biology underneath it has reasserted itself.

Together, shaping and instinctive drift mark the edges of conditioning. Shaping shows how flexible and powerful reinforcement can be for building new behavior from scratch. Instinctive drift shows that this flexibility has limits: biological predispositions constrain what can be permanently learned, connecting back to the broader idea that learning always operates on top of, not in place of, an organism's evolved nature.